If your Mac can work with a direct link to the pdf file, here's the dimensions for the W126:
http://www.startekinfo.com/StarTek/outside/12253/program/Engine/617/30-300.pdf I'm guessing it's the same as the W123.
Let me know if the link doesn't work for you. I tried to do the file as an attachment but it's too large for the forum requirements.